A speed ratio controller for a continuously variable transmission of a vehicle determines a target speed ratio from a vehicle speed, throttle opening or degree of accelerator depression, and upshifts or downshifts the transmission. Upshift characteristics include auto upshift, foot release upshift and foot return upshift.
Auto upshift is upshift performed when substantially constant depression is maintained after a drive depresses the accelerator pedal to accelerate the vehicle and vehicle speed is increased. Foot release upshift is upshift performed when the driver releases the accelerator pedal from any position while the vehicle is traveling. Foot return upshift is upshift performed when the driver decreases the degree of depression on the pedal so that the pedal returns to an intermediate position. Hence, even if the upshifts are the same, the running conditions under which they are performed are different.
The speed ratio controller disclosed by U.S. Pat. No 5,695,428, issued Dec. 9, 1997 determines whether an upshift is an auto upshift or foot release upshift based on the throttle opening TVO and the variation in the target speed ratio, and varies the response characteristics of the transmission according to the upshift characteristics.